Taccalonolides: Mechanisms of Action and Cellular Resistance

描述（由申请人提供）：微管稳定剂是用于治疗癌症的有价值的药物。该项目的重点是一类新的植物来源的微管稳定剂，taccalonolides。taccalonolides对间期微管集束，有丝分裂纺锤体形态和有丝分裂信号通路有明显的影响。有效的新的taccalonolides已被确定为第一次，他们稳健地纯化的微管，表明与微管蛋白/微管的直接相互作用。微管蛋白聚合实验还表明，taccalonolides与微管蛋白的相互作用的方式不同于其他微管稳定剂。我们的初步数据表明，taccalonolides结合在一个独特的网站微管蛋白。所有的他卡隆内酯都克服了临床相关的耐药性机制，并且他卡隆内酯A和E对紫杉醇和阿霉素耐药的乳腺癌小鼠模型具有体内抗肿瘤活性。全面的研究提出，以确定taccalonolides的微管蛋白结合位点，这种比宁的功能意义，以及如何中断有丝分裂和间期信号下游。这些研究有望确定一个新的微管蛋白结合位点或稳定微管的药效团。第一个目标是利用互补结构生物学方法确定taccalonolides在微管蛋白/微管上的结合位点。第二个目的描述了taccalonlavin与微管蛋白/微管生物化学和细胞中的相互作用的功能意义。 该目的将确定有效的taccalonolides对纯化的微管蛋白和细胞凋亡的影响。 微管动力学我们预期微管动力学的中断会导致有丝分裂信号传导和间期微管运输缺陷，最终导致细胞死亡。最后一个目的是研究taccalonolides的结构-活性关系，以确定最佳生物活性所需的特定化学部分。从这些研究中获得的信息将阐明这类新的微管稳定剂的化学和生物学性质。这有望导致一种新的微管稳定剂结合的鉴定 这将为合理的药物开发提供新的机会，并可能具有独特的活性谱。

DESCRIPTION (provided by applicant): Microtubule stabilizers are valuable drugs used in the treatment of cancer. The focus of this project is a new class of plant-derived microtubule stabilizers, the taccalonolides. The taccalonolides have distinct effects on interphase microtubule bundling, mitotic spindle morphology and mitotic signaling pathways. Potent new taccalonolides have been identified for the first time and they robustly polymerize purified tubuli indicating a direct interaction with tubulin/microtubules. The tubulin polymerization experiments also indicate that the taccalonolides interact with tubulin in a manner different from other microtubule stabilizers. Our preliminary data suggest that the taccalonolides bind within a unique site on tubulin. All of the taccalonolides overcome clinically relevant mechanisms of drug resistance and the taccalonolides A and E have in vivo antitumor activity against a paclitaxel and doxorubicin-resistant murine model of breast cancer. Comprehensive studies are proposed to identify the tubulin binding site of the taccalonolides, the functional significance of this bining and how this interrupts mitotic and interphase signaling downstream. These studies are expected to identify a new tubulin binding site or pharmacophore for stabilizing microtubules. The first aim will identify the binding site of the taccalonolides on tubulin/microtubules utilizin complementary structural biology approaches. The second aim describes the functional significance of the taccalonolide interaction with tubulin/microtubules biochemically and in cells. This aim will identify the effects of the potent taccalonolides on purified tubulin and on cellular microtubule dynamics. We anticipate that interruption of microtubule dynamics leads to mitotic signaling and interphase microtubule trafficking defects and ultimately cell death. The last aim will examine the structure-activity relationships of the taccalonolides to identify the specific chemical moieties necessary for optimal biological activities. Information gained from these studies will elucidate the chemical and biological properties of this new class of microtubule stabilizers. This is expected to lead to the identification of a new microtubule stabilizer binding site on tubulin that will provide new opportunities for rational drug development with the possibility of a unique spectrum of activity.